Electromagnetic switches



Jan. 28, 1958 F. E. ROMMEL 2,821,598

ELECTROMAGNETIC nSWITCHES vFiled Aug. L23. 1954 y s shuts-sheet 1 INveN-rok gm www@ g, m/We/m ATTORNEYS Jan. 28, 1958 F. E. ROMMEL 2,821,598

ELECTROMAGNETIC SWITCHES Filed Aug. 2s, 1954 3 shams-sheet 2 A lNvEN-rolz A, /am/ M477@ Y pw Air-roeNEYS Jan. 2s, 195s Filed Aug. 23,"1954 F. E. ROMMYEL ELECTROMAGNETIC SWITCHES 3 Sheets-Sheet 5 United States Patent O ice zszlsssr.

ELEcrRoMAGNETlc-SMTCHES;

Frederick-z Emil Rommel;v WestyDul-wiellrondona England, assignmltd; Telenhone,Manuacturirig; Company Limited, Londons Englanda ApplieationsAugiistZ'Sl, 1954*,l Seri'alfNo. 45153714'- Claiinsspi'inrilyaapplicatidnreat:BrifaimAllllStiZh.1953 'SPGlamsr @E200- 100;

This: inventiom relates. tos electrornagnetic` switchesV of the type employing a plurality of contact-sets,` apreselector: or so+callcd'fnger magnet pertaining to each contact; sett; andea maintoperaftingmagnet. Thew action is-xsuclnthat upon tenergisa'tion ofi a-ingermagnet amemf her; a whichi can be identiedf as an interference piece, *t is moved' into afposition'-such-thatwhen the main magnet is energised the= contacts of'the pertaining-setareactuated; thsetsrofwhichthedingenmagnets havemot beenpreviouslygy energiscd' arernot actuated; Switches of these types.; are used in. crossebar telephonesystems; onesuch switch isndescribediiniUnitediStates:Patent No.A 256730500, issuedi March 3; 1953, in'y the name. oftFredericlc- Ef. Rommel. Av switchy offfthi's type: istalso describedl ina co-.pendng Unitedi States:` applicationy No. 4513375 filed August: 23;.t 1954;. now: Batentf No; 2;&10,040. The present inventionrisaconcernediwithanv improvediconstruction of: switch.

In a switch of this-t typei the: design of. theI interferencepiece isi amatterofdieulty. In thetfirstplace crossnbar telephone-systems are=veryoftenlused-inaremote ruraligareas, so that? reliability.- over long periods-Vis of importance: even, more ,than in-y telephonez circuits ingeneralt. Secondly, as: will. be explained' inmore detail' here inaftere. the .interference .piecemustibe made sol astobe capable; of: substantially independent motions inftwo dilfectitns,` in; response.` to theL fingen magnet and to the maimrna-gnetfrespectively, butfatftheisame time any-movemont; which would. give r-isefto. incorrect-operation of `the ewitch mustrbe avoided'.

l'ltyisf convenient to, rean to. the twovmotions ofjthe interference; praderasi yhei-ngiin respectively the'l interfering direction, in.. which it: iswmovcd -by the` fingen magnet, and the actuating direction; in which it ismovedI by the mainlmagnet to causeactuation.y offtherelatedl contact Seti, In acrsiance with. theinvention', thereris-provided an electromagnetic; relay: comprising. a main operating magnet; a pluralityr of. Contact. sets, an` operator r`forthe contents Qfxeachfof-V saidcontact sets, avplurality ofdinger magnets: correspondingY to said. contact sets and each having4 anarmature carrying aninterf'erence piece arrangedon-operationo the ngermagnet to be movedin air-,interferingdirection; so asito be interposed between an actuator, moved' in an actuatingv direction by the armature ofthe main magnet,y and the operatori ofjthe correspnmdingl contact set and wherein guide? surfaces are proyidedV to limit. the, motion` of, each. Qf the. interference pieces in the actuating.,direction` when they'arernoved in the interfering. direction- 'approximately at -rright angles, and the interference piece 2,821,598 Patented Jan. 28, 1,958

2. isplimited; in its-movement in that direction which. isf at right. angles. toi both, of those directions.

Other. features and. advantages; of the invention, will appeal?,from thefollpwing description of this preferred embodmenttthereofi given byy way 0f example, in conjunction with the accompanying drawings. Thel switch shown; and tof be described,I isg of the` cross-bar type. referreditdfabovet vIn?the.'.drayvinas;

Figure,` 1 isasdeelevationof the switch;

Eigurel is a planiviewof the same switch;y

Eigvure) Sais .aniend elevation. ot theL switch;`

lig'ure.r 4\ isf al fragmentary .section onl the line x-.x of Figure 2;

vFisitrref ist aside View. 0nl an enlarged Scale, of: one Lof thejnserfmasnet arr-natures,` together with the-attached interference piece;

EigureA 6is an endview, on. an. enlarged. scale,v of the armatureandrinterfereneepieee QfFigureS;

Eigure] i's asidefvjeyy of animerference piece before Being. deformed, and..

Fivre. Seis aplanview of. thesuide block.-

"lh'e switch, shown, in these drawings` is built up on, a hase plate 1t).` o,f softlirlon. sheet; soft is to be under.- Stoddasmeanina material. of. high magnetic permeability and low. retenti'vity, such as4 is suitable for. use, with electromagnetic. devices.-

A-t its. one end. this baseplate has an. upwardly turned jange '10a which. Supports three. finger magnets. 11,; these masr'retshave dores llwhichare screwedinmandthrdush ange lila and there held by. l'ockrnitsl 1g; As willv be seen,v these magnets lie with their cores parallel to each otherv and to the bvaseplate. At the. otherend of the ibasepl'ate isanother 'flange 10b and three further iinger magnets 1-4have their cores 1'5screwed' into theV flange, and held" b-y-locknuts I6, The upper-edge of flange 10 b is: again turned* over, at 10c. The` cores of tinge;-` magrnetst`14 areA alsoqparaliel yto each other and to b'asepl'ate I0,y a-ndA the six--iingenmagnets all lie compactly-ifnione layer onthe baseplate:

At.- the sameY endf of they baseplate as ange- 10a isa fur-thenange'. 10d-g which servesito, carryy a main magnet; the maimmagnetcomprises a core t7 which. is butt welded to flange 10d; and upon. which is they operating coilf 20. "Ihegcoili is helda imposition on the` core by an internally .tQO.thedrspringI clip 2l; The armature for-thetmainmagnet includes. a; rectangular.,v elementl 22. of soft iron.` mounted uponv a carrier` 2133having a; substantially'venticalat. end 2.3.@ andv two sides 21312, 213e extend-ingv at right angles from it, one along each side on the switch. The. main armature 3f pivots.- On shaft 254 Secured to.-y a. generally inverted? Unhaned; saddle. lfxed to.y the fla-nge 10c-.- by screws. "1?0- the ends 01S the sides). 23h and*1 23p at Z1 and. 2.8,V is piyoted:v an` inverted U-shaped actuatorv 30, to whic t 1 further reference will be made; the-,base hasta depending. flange. 1.0.1y which. cooperates with.; armature of themain magnet,

The movement ofactuator 30 in the horizontal direef tion is limited' by 4arranging the horizontal' part. of f the actuator in a verticalslotor groove 31din a guide block 31 which liesfacrossthe basepl'ate, between the two rows of n-ger-magnets, and issecuredsto the baseplate, by screws 32:. Normally,- that,` isi` when' the main magnet is'notenergisedi the-horizontal#partofjthe actuator 30 lies wholly withinthe slotin, the guide block and in particular withits upperedge below the upper Surface Ofthe. block as shown int Figure 4: When. the manmagnet is energisedt. the upper edge of' the actuator risesabovelthis.surface.

Above the parts ofV theV switch thus so far describedY is a Contact assembly. Se far. as. the, constructions. support and actuation of'the contacts is concerned, this assembly 3. is generally as described in United States Patent No. 2,630,500, to which further attention is directed.

Briey, however, the assembly includes a mounting block 33 which is secured to the guide block 31 by screws 34, and sets of both stationary and moving contacts carried on this mounting block. The stationary contacts 35 are clamped in a stack of insulating spacers 36 and the moving contacts 37 are carried but not necessarily clamped in this stack. The stack is clamped to the mounting block by screws 38.

The moving contacts of each set are operated by a card 40; as shown there are seven sets of contacts each with its card. The moving contacts of each set enter slots in the edges of the card, and the cards are guided at their upper ends by means of a tongue-d spring plate 41, which provides a light downward bias pressure on the cards, and at their lower ends by a relatively rigid plate 42 secured to block 33 by screws 43.

The contact assembly forms a separate unit which can be attached to or removed from the rest of the switch, by means of the screws 34.

When the contact assembly is secured in position, all the cards 40 lie over the upper surface of guide block 31 in the relative lateral position shown in Figure 4. The lower edges of the cards are straight, as shown in Figure 4, and lie parallel to the upper surface of the guide block 31, but in the lowermost position of the cards, corresponding to the non-actuated condition of the contacts, the actuator 30 does not engage the lower edge of the cards of six of the contact sets, even when the main magnet is energised. The exception is the seventh set, which is that shown uppermost in Figure 2. The contacts of this set are the offnormal contacts; they have no nger magnet pertaining to them and they are actuated directly by the actuator 30 upon every energisation of the main magnet. These contacts are required in the circuit of a cross-bar system but hereinafter any reference to the contacts of the relay is to be taken as excluding these ofi-normal contacts.

So that one vertical set of contacts, pertaining to one finger magnet, can be operated by movement of its card, each finger magnet 11 has an armature which includes an armature element 44 and a spring arm 45, the latter carrying an interference piece 46, while the armatures of finger magnets 14 have correspondingly an element 47 and spring arm 48, the latter carrying an interference piece 50. Normally, that is with a finger magnet not energised, the interference pieces lie to one side of the actuator 30, as shown in Figure 2, the interference pieces 46 lying to the right and the interference pieces 50 to the left of the actuator. When any finger magnet is energised the corresponding armature moves, and the interference piece is brought into position immediately beneath the card 40 and over actuator 30, so that when the main magnet is energised the actuator raises the card and the contact set corresponding to the energised finger magnet is actuated.

It will be seen that the movement of thel interference pieces is limited in the actuating direction, that is, in the vertical direction in Figures 1 and 3; each interference piece is limited in its upward movement by the lower edge of the card 40, and in its downward movement by the surface of the guide block 31 upon which it normally rests.

` Additionally, and as shown more clearly in Figure 8, the upper surface of the guide block 31 is provided with a series of recesses or grooves 31a, one for each of the interference pieces 46, and corresponding recesses or grooves 31b for interference pieces 50. The lower part of the interference pieces is located, at all times, between the side walls of these recesses and so the interference pieces are likewise limited against movement in the direction at right angles to the interfering and, in this case also, the actuating direction, Since the recesses 31a and 31b have closed ends, the movement of the interference pieces in the interfering direction is also limited. The guide blocks 31 are also formed with webs 31e which lie between the adjacent armatures.

The armature elements of the finger magnet armatures are arranged to provide the necessary pivotal mounting for the armatures. The elements 44 or 47 are identical in construction through transposed in position in assembly and consist of a rectangular strip of soft iron of which one end is machined to a knife edge as shown at 44a and 37a in Figures 4, 5 and 6. To receive these knife edges, the baseplate is formed with two series of depressions 10e, 101, the depressions 10e for knife edges 44a and 10f for 47a. As will be appreciated from Figure 2, the depressions 10e are in line, and 10]c are likewise in line, and the two lines are parallel with each other. If desired, each row of depressions can be formed as a single elongated depression, but the separate depressions are preferred. Itis convenient to form the depressions by a pressing operation, in which case a hole may be formed in the metal before the pressing operation in order that the metal may iiow more easily.

The second parts of the armatures are the spring arms 45 and 48. These are also similar in shape, and are formed as stampings of spring material, such as Phosphor bronze or brass. As shown in Figures 5 and 6, spring 45 has a at portion 45a which lies against that face of the armature element 44 which is adjacent the core of the finger magnet, and a flange 45b along each edge to increase the stiffness of the spring. The spring is secured to its element by three small rivets 51. From the bottom edge of the flat portion 45a of the spring extend two small fingers 45C at right angles. These fingers, as will be seen from Figure 4, pass beneath the block 31, the centre part of which is cut away to receive the springs, and engage its under surface; thereby these spring fingers retain the armature elements in position in their respective depressions and they provide also the necessary restoring springs for the armatures.

The spring arms are also formed with bent-over extensions 45d or 48d which serve to carry at their extremities the interference pieces 46 or 50. A method found advantageous for attaching the interference pieces to those extensions is to make each interference piece as shown in Figure 7 as a short cylinder with a ange at one end and an intermediate narrow circumferential groove 46a. The end of each extension has a hole in it, with a slot leading from the hole to the end of the extension. The groove in the interference piece allows the latter to enter the slot and hence the hole, and the interference piece is then deformed endwise to cause it to be firmly and permanently clamped on the extension, and at the same time dimensioned within a close tolerance in the actuating direction.

In the co-pending application No. 451,375 further reference is made to the advantages which are obtained from the construction of finger magnet armature described above, but for the purpose of the present invention it has also the advantage that each armature member 45 or 48 supports the associated interference piece 46 or 50 with sufficient flexibility to allow it to be moved easily in the actuating direction, and also the interference piece to rest with light pressure on top of the guide block 31 in the energised condition of the finger magnet. This latter is an advantage because, as explained above, the contact assembly can be removed as a unit; this assembly includes the cards 40. When the contact assembly is removed in this way the interference pieces will continue to rest in position upon the guide block, and replacement of the assembly is facilitated.

In operation, the interference pieces are moved in two directions, the interfering direction and the actuating direction, as defined above. With the construction described the interfering direction is from left to right or right to left as seen in the view of Figure 4, while the actuating direction is up and ,down in this figure; clearly the interference piece must be capable of motion in these two directions. However, this freedom of movement is not in itself sufficient and it must be arranged that no damage will result if the main magnet is operated first, or if its operation is followed instead of preceded by the operation of the finger, and there must be no danger of incorrect operation of the switch in these circumstances.

The mounting of the interference piece on the resilient part of the finger magnet armature, thereby to permit the necessary movement in at least the actuating direction, is advantageous in this respect, but the danger would then normally arise that the interference piece if it moves excessively by the resilience of its carrier may foul some part of the switch and might not be drawn by the finger magnet into the correct position, and ncorrect actuation would result.

The construction of switch described avoids this difficulty, since the interference piece, within the limits of its motion in the interfering direction, is limited in its motion in the actuating direction. This will be clear from Figure 4; the lower edge of the card 40 and the upper surface of the block 31 parallel to it define a space within which the card is constrained to move.

In addition, the side walls of the recesses 31a and 31b in the top surface of the guide block 31 are engaged by the interference pieces at all times, so that each interference piece is limited in its movement not only in the actuating direction when it is moving in the interfering direction, but also in the direction at right angles to the actuating direction. Regarded in another way, the finger magnet armature moves its associated interference piece in the interfering direction, but in this movement, notwithstanding the flexibility of its support the interference piece is wholly guided, and it cannot escape from a prescribed path extending between the interfering and non-interfering positions.

Finally, the closed ends of the recesses 31a and 31b limit movement of the interference pieces in the interfering direction, as mentioned above.

By limiting the possible movement of the interference pieces by these various means the danger of misplacement of an interference piece is virtually eliminated and with it the possibility of incorrect operation due to this cause. This is an important practical advantage.

It is not necessary to adjust the extensions 45d, 48d carrying the interference pieces against the surface of the block 31 so that a critical contact pressure is obtained and this is also an important point in manufacture. It will be appreciated that as the actuator lies wholly below the surface of the block when the main magnet is not energised there is no obstruction to the movement of the interference piece, nor any danger of its failing to be inserted in proper position beneath the card. As a result a high degree of reliability is obtained. It is also to be observed that when the contact assembly is secured to the base plate the only operating spacing is that between the card and the surface block. This can be easily achieved in practice, and in any case the tolerance on this spacing is not excessive.

Thus the invention provides a construction of switch which is relatively cheap to manufacture, and of reliable operation.

I claim:

1. An electromagnetic switch device comprising a main operating magnet, a contact set, an operator for the contacts of the contact set, a finger magnet having an armature carrying an interference piece arranged to be moved in an interfering direction upon operation of said finger magnet so as to be interposed between said operator and an actuator arranged to be moved in an actuating direction by the armature of sai-d main magnet, and guide means providing guide surfaces eiective over the range of movement of said interference piece in the interfering direction to limit movement of said piece in directions at a substantial angle to the interfering direction without impeding movement of said piece in the interfering direction.

2. An electromagnetic switch device as defined in claim l wherein said operator has a substantially straight edge arranged substantially parallel to a guide surface provided by said guide means to define a guide space in which said interference piece is constrained to move.

3. An electromagnetic switch device as defined in claim l wherein said guide means includes a member providing a guide surface extending over the range of movement of said interference piece, said member being provided with a recess therein to receive said interference piece.

4. An electromagnetic switch device as defined in claim 1 wherein said guide means includes a member providing a guide surface extending over the range of movement of said interference piece, said member being provided with an elongated aperture therein providing an interruption in said guide surface, sai-d actuator being arranged to be moved through said aperture upon operation of said main magnet.

5. An electromagnetic switch device as defined in claim 4 wherein said member is provided with a recess therein to receive said interference piece, said recess extending across said elongated aperture at a substantial angle thereto.

6. An electromagnetic switch device as defined in claim 5 wherein said recess includes a terminal surface serving to limit movement of said interference piece in the interfering direction beyond the position in which it is interposed between said actuator and said operator.

7. An electromagnetic relay comprising a plurality of contact sets, an operator for the contacts of each of said contact sets, said operators being arranged in a row, a guide block below said row of operators, said guide block having a plurality of transverse, parallel spaced guide grooves located respectively in alignment with said operators and a second vertical groove extending at a right angle to said guide grooves and intersecting the same, said second groove extending in the direction of said row of operators, a main operating magnet, an actuator member disposed in said second groove of said guide block and movable upwardly upon energization of said main operating magnet, a plurality of finger magnets corresponding respectively to said plurality of contact sets, each of said finger magnets having an armature member actuated thereby and an interference piece carried by each armature, said interference pieces being received respectively by and slidably guided in said transverse guide grooves from a position to one side of said second groove and actuator when the corresponding finger magnet is unenergized to a position between said actuator and the corresponding operator when said finger magnet is energized whereby upon energization of said main operating magnet said actuator will be moved upwardly to engage and effect upward movement of those of said interference pieces which have been brought into alignment with said actuator lthereby effecting also upward movement of the corresponding operators to engage and actuate the corresponding contact sets.

8. An electromagnetic relay as defined in claim l wherein the transverse grooves in said guide block are closed at the end in the direction of movement of said interference pieces upon energization of said finger magnets.

References Cited in the file of this patent UNITED STATES PATENTS L S. DEPARTMENT OF COMMERCE PATENT OFFICE CERTIFICATE OF CORRECTION January 28;, 1958 Patent No, 2,821,598

Frederick Emil Rommel e printed specifi cation It is hereby oerified that error appears in th d that the said Letters of the above numberepatent requiring correction an Patent should read ascorrected below.

Column 6, line E, for the claim referenee numeral "l'1 read uw '7 n.,

Signed and seele this lst day oi April 1958,

(SEAL) Attest:

KARL H.. AXLINE ROBERT C. WATSON Comnissoner of Patents Attesting Officer i. S. DEPARTMENT 0F COMMERCE PATENT OFF I CE GRTIFICATE oF CORRECTION January 28, 1958 Patent No., 2,821,598 Frederick Emil Rommel It ie hereby certified that error appears in the printed specification of' the above numberedpatent requiring correction and that the said Letters Patent should read aecorrected below.

Column 69 line for the claim reference numeral nln read '7 Signed and eeale this lst day of April 1958@ (SEAL) Attest:

L H., AXLINE KAR ROBERT C. WATSON Comnssoner of Patents Atteetng Officer 

